Most vehicles utilize gasoline or diesel as fuels. There are, however, several well-known problems associated with using gasoline and diesel as fuels for vehicles. Many of these problems are associated with the emissions from combustion which contribute to unhealthy air pollution, global warming, and acid rain.
Another problem concerning gasoline and diesel as fuels for vehicles relates to the unequitable world-wide distribution of oil resources. Many countries rely heavily, if not completely, on the importation of oil to meet their demands for gasoline or diesel fuel.
Because of the well-known problems associated with gasoline and diesel as fuels for vehicles, much effort has gone into developing alternative fuels for vehicles in recent years. Natural gas is recognized as an alternative fuel to gasoline or diesel for vehicles. Natural gas has many advantages over gasoline or diesel as a vehicle fuel. Perhaps most importantly, natural gas burns much cleaner than gasoline or diesel fuel. It is also much less expensive than gasoline or diesel fuel for an equivalent energy content. Further, natural gas is safer because it rises and dissipates into the air, rather than settling like gasoline or diesel fuel. There are also engine performance benefits from using natural gas as a fuel. Natural gas has a higher octane as compared to gasoline, which will result in improved "cold starting" of vehicles.
To be used as an alternative fuel source for vehicles, natural gas is conventionally converted into compressed natural gas (CNG) or liquefied natural gas (LNG) in order to be able to store natural gas efficiently on board the vehicle. A variety of methods have been developed over the years to create CNG or LNG. Such known systems have traditionally been developed exclusive of one another. There remains a need to develop an improved system for producing both LNG and CNG and economically providing both LNG and CNG in an integrated fashion to a vehicle refueling station.
A primary barrier to using natural gas as a transportation fuel is the lack of a cost-effective refueling infrastructure. Although an abundance of natural gas network distribution lines exist in most geographic regions, no suitable system has heretofore been developed for converting low-pressure natural gas available through this distribution network into LNG and/or CNG, or a refueling infrastructure for providing LNG and/or CNG to end users. Traditional natural gas refueling systems commonly require the natural gas to be hauled in tanker trucks in a liquefied or compressed form.
The present invention involves an integrated refueling system for supplying LNG and CNG at vehicle refueling stations. The various objects, features and advantages of the invention will become apparent from the detailed description of the invention that follows.